Sometimes I get the feeling that I’m developing into the Orac of history of science and that I should concentrate on posting original thoughts on things mathematical or astronomical but then I stumble over something that however hard I try I simply can’t ignore. Then to ease the pain of indignation I just have to sit down at the keyboard and vent my spleen about the latest piece of inanity that has succeeded in provoking my ire.
Today via twitter my attention was drawn to “10 Astronomical Discoveries Made Without a Telescope” posted by a Shanna Freeman at Curiosity.com from Discovery, of itself a worthy endeavour. However upon closer examination the post proved to be rather less than perfect.
On the opening page we are presented with the image of an instrument, with the information, “The astrolabe was an important astronomical tool, used since at least 150 B.C.” Now I haven’t been able to identify the instrument displayed but of one thing I’m certain, it isn’t an astrolabe. The statement made is also repeated in the text and in the interest of accuracy I should point out that the oldest extant astrolabe is from the ninth century CE and although tradition attributes the invention of the astrolabe to Hipparchus, who lived in the second century BCE the earliest extant description of an astrolabe is from the sixth century CE.
Moving on to the 10 discoveries we find that the list includes solar eclipses, auroras, constellations and comets. Now you can call me pedantic but these are not what I understand under the word discovery. In fact if you were in the right place at the right time you would have to be literally blind not to notice a solar eclipse, an aurora or a comet. They were never discovered they occurred. Constellations is something completely different not only are they not discoveries they are not even natural. Constellations are artificial human constructs to help astronomer/astrologers find their way around the heavens.
In the text on solar eclipses we have the following wonderful statement:
However, exactly when the first solar eclipse occurred is a matter of dispute — aligning sometimes vague historical records with the exact date of an eclipse based on what we know of their cycle can be difficult.
The emphasised phrase should of course read, “exactly when the first solar eclipse observation was recorded…” Reading things like this explains why proofreaders and editors exist.
In the text on constellations we find the following:
However, the original 40 constellations described by Ptolemy in A.D. 150 were based on star lists on Babylonian cuneiform dating back to 687 B.C. In turn, this system was likely based on even earlier Sumerian concepts. Another 44 constellations were added over the years to create the system recognized by the IAU today.
Ptolemaeus lists 48 constellations and the IAU officially recognises 88 and in case you can’t do the arithmetic that’s another 40 that were added over the years.
Most of the text on heliocentricity is acceptable, with gritted teeth, but this half sentence is definitely not:
…but it took hundreds of years after Galileo for acceptance of heliocentrism to become widespread.
Within the scientific community heliocentrism had become generally accepted by about 1660, i.e. about twenty years after Galileo’s death.
Again the text on comets is OK with the exception of the last sentence:
Now that we can predict the orbit of Halley’s Comet (and other short-period comets), astronomers can use computer models to retrodict the comet’s orbit and match it to reported sightings.
You don’t need a computer to predict the orbit or periodicity of a comet. Comet Halley is called Comet Halley because Edmund Halley calculated its orbit and periodicity with a pencil and a piece of paper (he might have used a quill pen!) and the orbits and periodicities of several other comets were calculated over the two centuries between Halley’s work and the invention of the computer.
In general the text on sunspots is also OK except for an unfortunate typo, “Sunspots were not mentioned in Western literature in A.D. 807” should of course read “until A.D. 807.” However we have again one unacceptable sentence:
However, prior to Galileo, most of these observers believed they were seeing transits of planets in front of the sun.
A small number of historical pre-telescopic planet transits reports are now considered to be sunspot observations. There are however reports of disfigurements to the surface of the sun that are not recorded as planet transits.
Next up we have the subject of planetary movement and here our author gets into serious difficulties. First up we have the following:
Although it took thousands of years for astronomers to accept the theory of heliocentrism, ancient stargazers did become aware that the planets were rotating as well as orbiting around a central location.
Between Aristarchus (310 BCE – ca.230 BCE) and the acceptance of heliocentrism in about 1660 there are not quite two thousand years. Now one might again accuse me of pedantry but if somebody uses the expression “thousands of years” one usually understands significant more than two. Also the awareness of planetary rotation is a product of telescopic observation in the seventeenth century. It however gets worse:
The Greek astronomer Hipparchus accurately created geometric models of both lunar and solar motion in about 150 B.C. He measured angles using instruments that preceded the astrolabe and used trigonometry to make calculations. About 150 years later, Ptolemy, a Roman citizen living in Egypt, expanded upon the work of Hipparchus and others to create models of planetary movement. He also understood the retrograde motion — and that planetary orbits varied.
Not only did Hipparchus create models of planetary motion for all of the seven known planets, Sun, Moon, Mercury, Venus, Mars, Jupiter and Saturn but he was fully cognisant that those models need to explain retrograde motion. Even worse the same is true of the geometrical models of planetary motion created by Eudoxus, Callipus and Aristotle in the fourth century BCE.
Moving on we now have Neptune! A reminder the title of this post is “10 Astronomical Discoveries Made Without a Telescope”. Here the author produces the following strange paragraph:
Astronomers had been able to accurately predict the orbits of other planets like Jupiter and Saturn, but the orbit of Uranus had unexplained variations. Three days after astronomer Alexis Bouvard’s death in August 1846, another French cosmologist named Urbain Le Verrier announced that he had discovered the cause of Uranus’s perturbation: the gravitational pull of a previously unknown planet nearby. Le Verrier had spent nearly six months performing complex calculations before coming to this conclusion. Neptune’s existence was confirmed by telescope in September 1846.
Something is definitely missing from this paragraph! It reality Bouvard calculated the exact orbit of Uranus and from the irregularities in its orbit hypothesised the existence of another, not yet observed, planet. Both the English astronomer John Couch Adams and the French astronomer Urbain le Verrier calculated the theoretical orbit of the hypothesised planet from Duvard’s figures. Using le Verrier’s calculations Johann Gottfried Galle discovered Neptune with a telescope!
Moving on to the speed of light we hit a low point in this post. Ole Rømer determined the speed of light at the end of the seventeenth century using the determinations of the orbits of Galilean moons of Jupiter made by Cassini with a telescope!
The author’s final example is to put it mildly bizarre, radio astronomy. She describes the discovery of interstellar radio waves by Karl Jansky but somehow neglects to mention that radio astronomy is conducted using radio telescopes!
The post that I have ridiculed above appeared on a major commercial website that almost certainly attracts a lot of traffic. The post is supposed to be both informative and educational but what we have is full of errors, badly written and badly edited. It’s posts like this that give the Internet a bad reputation amongst professional educators. “Don’t use the Internet its only full of false information”. Those of us who care about the Internet as an educational medium should make it our duty to pillory such posts and their authors and force them either to correct their rubbish or delete it.